Vulnerability Note VU#106392

Overview

There is a denial-of-service vulnerability in several specific but common configurations of Cisco IOS.

Description

There is a problem involving BGP updates on Cisco routers with BGP4 Prefix Filtering and Inbound Route Maps enabled. A route update with an unrecognized transitive attribute may cause vulnerable routers to crash. This problem does not appear to have been exploited intentionally by attackers, but it has occurred accidentally during normal operation as the result of interaction with another vendor's product.

Impact

Attackers that are able to send malformed BGP updates can cause vulnerable routers to crash causing network outages. Under certain circumstances, an attacker may be able to use the BGP infrastructure to propogate the bad route update to multiple routers.

Solution

Cisco has released an advisory that provides a list of affected products, along with instructions for obtaining fixed software. Because there are many possible combinations of hardware and software configurations, the CERT/CC recommends that all users of IOS and software consult the following Cisco Security Advisory: